Surface light source device

ABSTRACT

A surface light source is provided which can press and attach a light source on a light-conductor plate in a manner not to cause a predetermined gap or more at between the light source and the light-conductor plate.  
     Fixture-fit areas  49  are recessed on the both sides in the upper and lower surfaces of a light-source receiver  47  provided in a light-conductor plate  33,  to provide snaps  50  projecting in the fixture-fit areas  49.  Between the fixture-fit area  49  and the light-source receiver  47,  formed are clamp steps  51  equal in depth to the fixture-fit area  49.  Clamp steps  42  are recessed on the both sides in the upper and lower surfaces of the point light source  32  put in the light-source receiver  47.  The metal fixture  52  is attached to the light-conductor plate  33  by engaging, on the snaps  50,  the engaging holes  54  of the fit pieces  53  provided in the metal fixture  52.  The clamp steps  51, 42  are clamped together by the upper and lower clamp pieces  55  provided in the metal fixture  52,  thereby holding the point light source  32  with alignment thicknesswise of the light-conductor plate  33.  Furthermore, by urging abutment pieces 56 of the elastically deflected metal fixture  52  on a backside of the point light source  32,  the point light source  32  is urged on a light incident surface of the light-conductor plate  33.

TECHNICAL FIELD

The present invention relates to surface light source devices. Moreparticularly, the invention relates to a surface light source device foruse as a backlight, a front-light or the like for a liquid-crystaldisplay or other display apparatuses.

BACKGROUND ART

Conventionally, various displays including liquid-crystal displays usesurface light source devices as backlights, front-lights and the like.For liquid-crystal displays featured small in thickness and light inweight, there are increasing demands for the displays of personalcomputers, etc. However, no light emissions occur on the liquid-crystalpanel per se, external light or a supplementary light source is requiredin order to view the content being displayed. Meanwhile, there arerecent needs toward thickness reduction and power saving due to greatlyincreasing demands for liquid-crystal displays on the mobile devicessuch as cellular phones and PDAs. For this reason, efficient utilizationof light is of a problem of importance.

Under the technical background like the above, transition is graduallyfrom those using so-called linear light sources, such as cold cathodetubes to surface light sources using LEDs (light-emitting diodes). Thereis a desire to construct a surface light source device with using LEDsin the number to a possible small extent.

The surface light source device using so-called a point light source isbased on the principle that the light emitted from a point light sourceis introduced to the interior of a light-conductor plate through itslight incident surface, and spread throughout the light-conductor platewhile being totally reflected at between the main and back surfaces ofthe light-conductor plate. By a polarization pattern formed in thebackside of the light-conductor plate, the light is caused to exittoward the front so that the light can exit at the surface of thelight-conductor plate.

FIG. 1(a) is a plan view showing a structure of a conventional surfacelight source device 1, FIG. 1(b) is a cross-sectional view on line X-Xin FIG. 1(a), and FIG. 1(c) is a bottom view of the surface light sourcedevice 1. In the surface light source device 1, a point light source 2resin-encapsulated with an LED chip is mounted on a flexible printedboard 4 by use of solder 3. The flexible printed board 4 is opened witha crimp hole 5. The light-conductor plate 6, a transparent resin mold,is formed with a light-emission window 7 in a corner thereof. In thevicinity of the light-emission window 7, a crimp pin 8 projects in anunderside of the light-conductor plate 6. The point light source 2 isinserted in the light-emission window 7 of the light-conductor plate 6,and the crimp pin 8 is inserted through the crimp hole 5 of the flexibleprinted board 4. The crimp pin 8 is heated and crushed thereby effectingthermal crimping and fixing the point light source 2 onto thelight-conductor plate 6.

However, in the surface light source device 1 of such a structure, incase the light-emission window 7 of the light-conductor plate 6 and thepoint light source 2 are the just equal in size, there is a difficultyin automatically inserting the point light source 2 in thelight-emission window 7. Thus, a slight clearance is provided to betweenthe point light source 2 and the light-emission window 7. Consequently,in the state the point light source 2 is mounted, a gap occurs between afront surface (light-emission window) of the point light source 2 and awall surface (light incident surface) of the light-emission window 7. Asshown in FIG. 2, light leak readily occurs through the gap toward themain and back surfaces of the light-conductor plate 6, thus making itimpossible to efficiently introduce the light emitted from the pointlight source 2 into the light-conductor plate 6. Thus, there is aproblem of lowering in light utilization efficiency. Particularly, onthe surface light source device using a point light source 2, such lightleak is to cause a great reduction of light utilization efficiencybecause the emission light amount at light source is lower as comparedto the cold cathode tube or the like.

Meanwhile, in such a surface light source device 1, the flexible printedboard 4 is thermally crimped by the crimp pin 8, the crimp pin 8 isconsiderably long in projection length even after thermal crimping ifconsidering a setup strength. Usually, the thickness d in the crimpingportion is as great as 0.3 mm. Consequently, the thickness of thesurface light source device 1 overall including the crimp pin 8 issignificantly great as compared to the thickness of the light-conductorplate 6 itself in the region other than the crimp pin 8, resulting in anincreased thickness of the entire surface light source device 1 andhence a difficulty in reducing the thickness thereof.

Furthermore, in such a surface light source device 1, because the pointlight source 2 in plan is aligned with the light-emission window 7, thepositional accuracy in plan thereof is favorable. However, in thedirection thicknesswise of the light-conductor plate 6, the point lightsource 2 is aligned by abutting the flexible printed board 4 against anunderside of the light-conductor plate 6. There undergo affections dueto the variation, etc. in thickness of a solder 3 and inclination of anLED chip mounted, resulting in deviation in positional accuracy of thepoint light source 2 in the height direction. In case such variation inthe height direction exists where a gap like the above is occurringbetween the front surface of the point light source 2 and the wallsurface of the light-emission window 7 as mentioned above, light leakincreases thus resulting in a problem of further lowering in lightutilization efficiency.

For this reason, in order to eliminate the gap of between the frontsurface of the point light source 2 and the wall surface of thelight-emission window 7, there is a proposal that a projection 9protruding from the wall surface of the light-emission window 7 isabutted against a backside of the point light source 2 to thereby urgethe front surface of the point light source 2 on the wall surface of thelight-emission window 7. This structure can decrease the leak of thelight emitted from the point light source 2. However, even thisstructure still requires a crimp pin 8 thus not solving the problem thatthe surface light source device 1 is increased in thickness into adifficulty to reduce the thickness.

Meanwhile, there are strong demands for device thickness reduction asseen in portable appliances, which inevitably imposes the need to reducethe thickness of the surface light source devices correspondingly. Theconventional surface light source device has the overall thickness of1.3 mm. Recently, demand is for a surface light source device having athickness of 1.0 mm or smaller even at its point light source portion.Subtracting a flexible printed board thickness of 0.2 mm therefrom, thepoint light source must be suppressed 0.8 mm or smaller in thickness.There are a variety of proposals on the thickness reduction for thesurface light source device. However, in the method of thermal crimpingby placing the point light source 2 within the light-conductor plate 6as in the surface light source device 1 shown in FIG. 1, the regioncrimped is as thick as 0.3 mm. Excepting the thickness of the crimpingregion and the thickness of the flexible printed board 4, there is aneed for a point light source to have a thickness of 0.5 mm or smaller.At present, the point light source of side emission is minimally 0.6 mmthick.

In a surface light source device 10 shown in FIG. 4, a recess 11 isformed in an outer peripheral surface of a light-conductor plate 6, toarrange a point light source 2 in a manner opposing to the recess 11. Areflective sheet 12 is bonded between an upper surface of the pointlight source 2 and the upper surface of the light-conductor plate 6while a reflective sheet 12 is bonded also between the lower surface ofthe point light source 2 and the lower surface of the light-conductorplate 6.

With this method, the light, emitted from the point light source 2 tothe above of the surface of the light-conductor plate 6 or to the belowof the back surface of the light-conductor plate 6, can be reflectedupon the reflective sheet 12 and guided to the light-conductor plate 6,as shown in FIG. 5, which improves light utilization efficiency.However, in this method, the point light source 2 and light-conductorplate 6 are not sufficiently aligned before bonding the reflective sheet12. In case variations occur in the gap between the point light source 2and the light-conductor plate 6 due to the variation in bonding thereflective sheet 12, there is a decrease in the light introduced intothe light-conductor plate 6 thus lowering light utilization efficiency.Furthermore, because the reflective sheet 12 is bonded on the bothsurfaces of the light-conductor plate 6, the surface light source device10 increases in thickness. In addition, components increase in thenumber.

Meanwhile, in a surface light source device 17 shown in FIG. 6,snap-formed fitting holes 19 partly cut away are previously provided ina flange 18 formed of an exterior resin of a point light source 2. Asshown in FIG. 7, the flange 18 with the point light source 2 is fittedover the outer peripheral surface of the light-conductor plate 6 in amanner covering a region a recess 11 is formed. By elastically fittingthe fitting holes 19 of the point light source 2 with the fitting pins20 projecting on the both surfaces of the light-conductor plate 6, thepoint light source 2 is fixed. However, even on this surface lightsource device 17, where there occur variations in the gaps between thepoint light source 2 and the light-conductor plate 6 due to errors inthe fitting holes 19 or fitting pins 20, the light introduced to thelight-conductor plate decreases to lower the light utilizationefficiency. Furthermore, because the flange 18 is laid over the bothsurfaces of the light-conductor plate 6, the surface light source device17 increases in thickness.

Meanwhile, in a surface light source device 21 shown in FIG. 8, crimpholes 22 are previously opened in both sides of a point light source 2as shown in FIG. 9. After inserting the crimp pins 23 projecting in anouter peripheral surface of the light-conductor plate 6 into the crimpholes 22 of the point light source 2, the crimp pins 23 are thermallycrimped to thereby attach the point light source 2 to thelight-conductor plate 6. However, in this surface light source device21, a gap readily occurs at between the point light source 2 and theouter peripheral surface of the light-conductor plate 6 due tovariations in thermal crimping. There is a problem that, if a gapoccurs, light leaks through it thus lowering light utilizationefficiency.

With the surface light source device of a structure attaching a pointlight source on the outer peripheral surface of light-conductor plate asabove, there is a fear to cause a gap at between the point light sourceand the light-conductor plate, thus involving a problem that light leaksthrough the gap thus worsen the light utilization efficiency and whereinthe structure is not resistive to impacts.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a slim-type surfacelight source device that, even in the case of attaching a light sourceto an outer surface of a light-conductor plate, the light source can beurged and fixed on the light-conductor plate in a manner not causing apredetermined gap or greater at between the light source and thelight-conductor plate without increasing the thickness of thelight-conductor plate.

A surface light source device according to the invention ischaracterized by comprising: a light-conductor plate that conducts lightat an interior and allows the same to exit at a light-exit surface to anoutside; and a light source arranged oppositely to a light incidentsurface of the light-conductor plate; the light source being held by afixture engaged on the light-conductor plate, the fixture in part beingelastically abutted against a surface of the light source opposite tothe light conductor plate.

In the surface light source device of the invention, the light source isheld by a fixture engaged on the light-conductor plate while the fixtureat a part is elastically abutted against a surface of the light sourceopposite to the light conductor plate. Accordingly, the light source canbe urged on the light incident surface of the light-conductor plate,thus preventing a required gap or greater from occurring at between thelight incident surface of the light-conductor plate and the lightsource. Consequently, the light of the light source less leaks due to anincrease of the gap between the light-incident surface of thelight-conductor plate and the light source, thus improving the lightutilization efficiency on the surface light source device. Moreover, thesurface light source device can be reduced in thickness. Meanwhile, theuse of the fixture improves the resistance to impacts upon attaching thelight source and facilitates assembling of the surface light sourcedevice, thus lowering component cost.

Meanwhile, in an embodiment of a surface light source device of theinvention, the light-emission window of the light source desirably has aheight equal to or smaller than a thickness of the light-conductorplate. In case the light-emission window of the light source has aheight equal to or smaller than a thickness of the light-conductorplate, the light emitted from the light source enters the interior ofthe light-conductor plate without leaking to an outside of the lightsource and light-conductor plate, thus improving the light utilizationefficiency on the surface light source device.

Likewise, in another embodiment of a surface light source device of theinvention, the fixture desirably has an exterior height equal to orsmaller than a thickness of the light-conductor plate. In case thefixture has a height equal to or smaller than a thickness of thelight-conductor plate, the fixture can not protrude from the upper orlower surface of the light-conductor plate, thus reducing the thicknessof the surface light source device.

Likewise, in still another embodiment of a surface light source deviceof the invention, the fixture is featured having a shape symmetric in180-degree-rotation about an attaching direction to the light-conductorplate. Accordingly, because the fixture is free of directivity in shape,there is no need to selectively arrange the upside/downside of thefixture upon attaching the fixture to the light source or thelight-conductor plate, thus simplifying assembling process.

Meanwhile, in yet another embodiment of a surface light source device ofthe invention, the fixture may be removably fixed on the light-conductorplate. In case the fixture is is removable from the light-conductorplate, when the light source or the light-conductor plate is replaced orrepaired, the fixture can be removed from the light-conductor plate tothereby separate the light source and the light-conductor plate.Meanwhile, the light source and the light-conductor plate can beassembled together by using again the same fixture. Accordingly, thefixture can be reused. In addition, the repairability of the surfacelight source device is improved.

In order to make the fixture removable, the fixture may be fixed on thelight-conductor plate by recessing fixture-fit areas in upper and lowersurfaces of the light-conductor plate, providing catches projecting inthe fixture-fit areas, providing fit pieces in a ring form, an L-form orT-form in the fixture formed in a folded-double form, and putting thefit pieces on the fixture-fit areas into engagement on the catches, forexample. In such a structure, because the fit piece of the fixture ismerely engaged on the catch of the light-conductor plate, the fixturecan be easily removed by disengaging the fit piece of the fixture fromthe catch. Meanwhile, because the fit piece is put in the fixture-fitarea recessed in the light-conductor plate, the fit piece can beprevented from protruding from the light-conductor plate.

Otherwise, in order to make the fixture removable, the fixture may befixed on the light-conductor plate by providing catches in a sidesurface of the light-conductor plate, and engaging, on the catches, thefit pieces in a ring form, an L-form or T-form provided in the fixture.Incidentally, the side surface of the light-conductor plate is notlimited to the side surface of the light-conductor plate entirety butmay be a side surface of an extended region in an outer peripheralsurface of the light-conductor plate. In such a structure, because thefit piece of the fixture is merely engaged on the catch of thelight-conductor plate, the fixture can be easily removed by disengagingthe fit piece of the fixture from the catch. Meanwhile, because the fitpiece is engaged on the catch at the side surface of the light-conductorplate, the fit piece can be made not protruding from the light-conductorplate by providing the height of the fit piece lower than the thicknessof the light-conductor plate.

Meanwhile, in yet another embodiment of a surface light source device ofthe invention, the fixture may be fixed on the light-conductor plate byforming one of a crimp projection or crimp hole in any of a fixture-fitarea recessed in an upper surface or a lower surface of thelight-conductor plate, a side surface of the light-conductor plate and afront surface of the light-conductor plate, forming other of the crimpprojection or the crimp hole in the fixture, and inserting the crimpprojection in the crimp hole into crimping. In this form, the fixture isattached to the light-conductor plate by crimping the crimp projection.However, because the crimp projection or crimp hole on thelight-conductor plate side is provided in any of the fixture-fit arearecessed in the upper or lower surface of the light-conductor plate, theside surface of the light-conductor plate and the front surface of thelight-conductor plate, the crimp projection, etc. does not protrude fromthe upper or lower surface of the light-conductor plate, thus reducingthe thickness of the surface light source device.

Meanwhile, in yet another embodiment of a surface light source device ofthe invention, the fixture and the light-conductor plate may havealigning means for aligning the fixture and the light-conductor plate toeach other thicknesswise of the light-conductor plate, the fixture andthe light source having aligning means for aligning the fixture and thelight source to each other thicknesswise of the light-conductor plate.According to the embodiment, because the light source and thelight-conductor plate can be aligned with each other thicknesswisethrough the fixture, the light source can be prevented from deviatingthicknesswise relative to the light-conductor plate thereby readilyleaking light, thus improving the light utilization efficiency.

As means for aligning the fixture and the light-conductor plates thereis a method of providing a thickness-reduced portion in a vicinity ofthe light incident surface of the light-conductor plate, and clampingthe thickness-reduced portion by a pair of parallel protuberancesprovided in the fixture. According to this means, because thethickness-reduced portion of the light-conductor plate is clamped by thefixture, the fixture clamping the light-conductor plate does notincrease in height, thus reducing the thickness of the surface lightsource device.

Meanwhile, as another means for aligning the fixture and thelight-conductor plate, there is another method of forming one of apositioning projection or a positioning hole in any of a recess providedin an upper surface or an lower surface of the light-conductor plate, aside surface of the light-conductor plate and a front surface of thelight-conductor plate, forming other of the positioning projection orthe positioning hole in the fixture, and fitting the positioningprojection in the positioning hole. According to this means, thepositioning projection or the positioning hole does not protrude fromthe upper or lower surface of the light-conductor plate. Due to this,the fixture height can be provided within the thickness of thelight-conductor plate, thus reducing the thickness of the surface lightsource device.

Meanwhile, as means for aligning the fixture and the light source, thereis a method of providing a thickness-reduced portion at least in a partof the light source, and clamping the thickness-reduced portion by apair of parallel protuberances provided in the fixture. According tothis means, because the thickness-reduced portion of the light source isclamped by the fixture, the fixture clamping the light source does notincrease in height, thus reducing the thickness of the surface lightsource device.

Meanwhile, as another means for aligning the fixture and the lightsource, there is a method of forming one of a positioning projection ora positioning hole in any of a recess provided in an upper surface or anlower surface of the light source, a side surface of the light sourceand a front surface of the light source, forming other of thepositioning projection or the positioning hole in the fixture, andfitting the positioning projection in the positioning hole. According tothis means, the positioning projection or the positioning hole does notprotrude from the upper or lower surface of the light source. Due tothis, the fixture height can be provided within the thickness of thelight source, thus reducing the thickness of the surface light sourcedevice.

Meanwhile, as still another means for aligning the fixture and the lightsource, there is a method of forming a positioning slit in a backsurface of the light source, and fitting a part of the fixture in thepositioning slit. According to this means, the structure for fitting thefixture and light source together can be made small in thickness, thusreducing the thickness of the surface light source device.

Incidentally, the constituent elements explained above of the inventioncan be combined to a possible extent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (a) is a plan view showing a structure of a conventional surfacelight source device, (b) a cross-sectional view on line X-X in (a), and(c) a bottom view of the surface light source device.

FIG. 2 is a magnifying cross-sectional view explaining the manner oflight leak through a gap between a light-conductor plate and a pointlight source in the surface light source device.

FIG. 3 is a magnifying cross-sectional view explaining a method toprevent a gap from occurring at between a light-conductor plate and apoint light source in a conventional surface light source device.

FIG. 4 is a perspective view showing a part of the conventional surfacelight source device having a point light source attached outside thelight-conductor plate.

FIG. 5 is a cross-sectional view showing a part of the surface lightsource device.

FIG. 6 is an exploded perspective view showing a part of anotherconventional surface light source device having a point light sourceattached outside the light-conductor plate.

FIG. 7 is a cross-sectional view showing a part of the surface lightsource device.

FIG. 8 is an exploded perspective view showing a part of still anotherconventional surface light source device having a point light sourceattached outside the light-conductor plate.

FIG. 9 is a perspective view of a point light source used on the surfacelight source device.

FIG. 10 is a schematic perspective view of a surface light source deviceaccording to embodiment 1 of the invention.

FIG. 11 is a plan view showing a structure of a region (extended region)where a point light source is attached, in the surface light sourcedevice.

FIG. 12 is an exploded plan diagram of FIG. 11.

FIG. 13 is a side view of a point light source and metal fixture.

FIG. 14 is a perspective view, partly broken away, of a state the metalfixture is removed from the light-conductor plate, in the surface lightsource device of FIG. 10.

FIG. 15 is a perspective view, from back, of the point light source usedon the surface light source device.

FIG. 16 is a cross-sectional view of the point light source.

FIG. 17 is a magnifying perspective view, partly broken away, showing astate that a fit piece of a metal fixture is attached to a snap of thelight-conductor plate.

FIG. 18 is a figure showing a relationship between a positionaldeviation δ in a height direction of the point light source andlight-conductive plate, and an incident loss thereof.

FIG. 19 is a figure showing a relationship between a deflection amountof the metal fixture ξ and a magnitude of its reactive force P.

FIG. 20 is a figure explaining a deflection amount of the metal fixtureξ and a magnitude of its reactive force P.

FIG. 21 is a perspective view showing a different shape of a point lightsource to be used in the embodiment.

FIG. 22 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 2 of theinvention.

FIG. 23 is a perspective view of a point light source used on thesurface light source device.

FIG. 24 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 3 of theinvention.

FIG. 25 is a perspective view of a point light source used on thesurface light source device.

FIG. 26 is a magnifying perspective view showing a part of a surfacelight source device having a fit piece in a different shape.

FIG. 27 is a plan view of the metal fixture.

FIG. 28 is a magnifying perspective view showing a part of a surfacelight source device having a fit piece in a further different shape.

FIG. 29 is a plan view of the metal fixture.

FIG. 30 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 4 of theinvention.

FIG. 31 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 5 of theinvention.

FIG. 32 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 6 of theinvention.

FIG. 33 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 7 of theinvention.

FIG. 34 is perspective view showing, with magnification, a part of asurface light source device according to embodiment 8 of the invention.

FIG. 35 is an exploded perspective view showing, with magnification, apart of the surface light source device according to embodiment 8.

FIG. 36 is an exploded perspective view in a different directionshowing, with magnification, a part of the surface light source deviceaccording to embodiment 8.

Incidentally, the major references used in the drawings are as follows.

31 surface light source device

32 point light source

33 light-conductor plate

35 light incident surface

41 projection

42 clamp step

43 push area

46 extended region

47 light-source receiver

48 projection

49 fixture-fit area

50 snap

51 clamp step

52 metal fixture

53 fit piece

54 engaging hole

55 clamp piece

56 abutment piece

61 crimp pin

63 positioning slit

64 positioning projection

65 crimp hole

66 positioning hole

BEST MODE FOR CARRYING OUT THE INVENTION

Hereunder, embodiments of the present invention will be explained indetail. Note that the invention is not limited to the followingembodiments but, naturally, is to be modified within the scope notdeparting from the technical idea of the invention.

Embodiment 1

FIG. 10 is a schematic perspective view of a surface light source device31 according to embodiment 1 of the invention. The surface light sourcedevice 31 is made up by a point light source 32 and a light-conductorplate 33. The point light source 32 is fixed on an outer peripheralcorner of the light-conductor plate 33 rectangular in form by means of ametal fixture 52. In a lower surface of the light-conductor plate 33,there are recessed a plurality of polarization patterns 34 triangular incross section. The polarization patterns 34 are arranged nearlyconcentric with spacing about a light-emission point of the point lightsource 32. Consequently, in case light is emitted from the point lightsource 32 incorporating therein a light emitting element such as an LEDchip, the light from the point light source 32 enters thelight-conductor plate 33 at a light incident surface 35 (see FIG. 12) ofthe light-conductor plate 33 opposed to the point light source 32, andspreads nearly throughout the light-conductor plate 33 while repeatingtotal reflections within the light-conductor plate 33 at between itsmain and back surfaces. In case the light in the light-conductor plate33 is incident upon the polarization pattern 34 in the course ofpropagation through the light-conductor plate 33, the light incidentupon the polarization pattern 34 is totally reflected by thepolarization pattern 34 toward the main surface while the light,incident upon the main surface of the light-conductor plate 33 at anangle smaller than a critical angle of total reflection, is allowed toexit the surface (at a light-exit surface 36) of the light-conductorplate 33. Here, the polarization patterns 34 have an arrangement in adensity designed with a distance, etc. of from the point light source 32such that the light exiting the light-exit surface 36 is nearly uniformin intensity throughout the effective region of the light-conductorplate 33.

Incidentally, in some cases, a reflective sheet, such as an Ag film or awhite resin sheet, is arranged over the lower surface of thelight-conductor plate 33 in order to return the light leaked through theback surface of the light-conductor plate 33 into the light-conductorplate 33. Meanwhile, a diffusive sheet maybe properly arranged over theupper surface of the light-conductor plate 33.

Now, explanation is made on an attachment structure of the point lightsource 32 in the surface light source device 31. FIG. 11 is a plan viewshowing an attachment structure of the point light source 32 in thesurface light source device 31, FIG. 12 an exploded plan view thereof,FIG. 13 a side view of the metal fixture 52 and point light source 32 asviewed laterally, FIG. 14 a perspective view of a state the metalfixture 52 is removed from the light-conductor plate 33. Meanwhile, FIG.15 is a perspective view of the point light source while FIG. 16 is across-sectional view of the point light source. FIG. 17 is a magnifyingperspective view, partly broken away, showing a state the metal fixture52 is attached on the light-conductor plate 33.

The point light source 32 has a structure as shown in FIGS. 15 and 16.In the point light source 32, a light emitting element 37 such as an LEDchip mounted on a stem (not shown) is encapsulated in a transparentresin 38. Furthermore, the transparent resin 38 is covered with a whiteexterior resin 39, in a region excepting its front surface so that thelight emitted at the light emitting element 37 can exit only through alight-emission window, a transparent resin region at a part in front ofthe point light source 32. The exterior resin 39 is formed with afixture engager 40 of resin, in a back surface thereof. The fixtureengager 40 is provided, at its both sides, with projections 41 smallerin thickness than the exterior resin 39. The projection 41 has upper andlower surfaces the respective ones of which are receded relative to theupper and lower surfaces of the exterior resin 39, thus forming clampsteps 42. A push area 43 is recessed centrally in a backside of thefixture engager 40. As shown in FIGS. 16 and 14, the point light source32 is mounted on a flexible printed board 45 by a solder 44. Note thatreference 32a is a terminal for energizing to the point light source 32.

An extended region 46 is provided in the corner of the light-conductorplate 33. The extended region 46 protrudes in a diagonal direction ofthe light-conductor plate 33 and has a side nearly parallel with thedirection orthogonal to the diagonal direction of the light-conductorplate 33. In a center of the extended region 46, a light-source receiver47 is recessed nearly rectangular in form in a manner penetratingthrough between the both surfaces. Furthermore, as shown in FIG. 12, alight incident surface 35 slightly recessed is formed in a deep surfaceof the light-source receiver 47. In the light incident surface 35, amultiplicity of micro-prisms (not shown) are formed in order tointroduce the light of from the point light source 32, at a wide angle,into the light-conductor plate 33. Furthermore, abutment surface 60 isprovided protruding, against the point light source 32, on the bothsides of the light incident surface 35 in order not to deform themicro-prisms due to hitting of the point light source 32 upon the lightincident surface 35 after assembling. Meanwhile, in an inner peripheralside face of the light-source receiver 47, a projection 48 is providedin order to prevent the point light source 32 from chattering left andright due to an abutment thereof against a side surface of the pointlight source 32 put in the light-source receiver 47.

Meanwhile, on both sides of the light-source receiver 47, fixture-fitareas 49 are recessed respectively in the both surfaces of the extendedregion 46. Claw-formed snaps 50 (catches) project respectively in thefixture-fit area 49 in the left and right, main and back surfaces. Thesnap 50, at its rear half, is formed with a slant surface 59 formedslanted rearward. The snap 50 has a height smaller in dimensions thanthe depth of the fixture-fit area 49 so that the snap 50 does notproject out of the surface of the light-conductor plate 33. Meanwhile,clamp steps 51 are formed in the both surfaces of the extended region46, in areas between the light-source receiver 47 and the fixture-fitareas 49. Here, thickness is nearly equal to between thethickness-reduced portion of between the fixture-fit area 49 in the bothsurfaces and the thickness-reduced portion of between the clamp steps 51in the both surfaces. Incidentally, the thickness-reduced portion ofbetween the clamp steps 42, in the both surfaces of the point lightsource 32, has a thickness (thickness of the projection 41) also nearlyequal to the thickness of the thickness-reduced portion between thefixture-fit area 49 and to the thickness of the thickness-reducedportion between the clamp steps 51.

Consequently, in case the point light source 32 is fit in thelight-source receiver 47 of the light-conductor plate 33, the projection48 abuts against the side surface of the point light source 32, tothereby align the point light source 32 left and right. This eliminatesthe chatter of the point light source 32 leftward and rightward.Meanwhile, the point light source 32 has a depth equal in dimensions tothe depth of the light-source receiver 47 so that, when the point lightsource 32 is fit in the light-source receiver 47, the point light source32 in part thereof (e.g. at the tip of the projection 41) is flush withthe end face of the extended region 46 as shown in FIG. 14. Because thepoint light source 32 is fixed on the flexible printed board 45 by asolder 44 as noted before, fitting the point light source 32 in thelight-source receiver 47 places the flexible printed board 45 intoabutment against the lower surface of the light-conductor plate 33, thusmaking it impossible to remove the point light source 32 upward from thelight-source receiver 47 and hence roughly aligning the point lightsource 32. In this state, the region, extending over from thefixture-fit area 49 to clamp step 51 of the light-conductor plate 33 andto the clamp step 42 of the point light source 32, has a thicknesssmaller than but nearly equal to the thickness of the light-conductorplate 33.

The point light source 32, fit in the light-source receiver 47 of thelight-conductor plate 33, is fixed on the light-conductor plate 33 bythe metal fixture 52. The metal fixture 52 is fabricated by blanking andthen bending a metal material, e.g. a stainless steel sheet, a steelsheet or an aluminum sheet, having a shape symmetric upper and lower andleft and right. The metal fixture 52 is folded double with spacing intoa U-form in cross-section, which has a gap height of between the upperand lower halves equal to the thickness of the thickness-reducedportions between the both surfaces of the fixture-fit area 49, clampsteps 51 and clamp steps 42.

The metal fixture 52 is provided with fit pieces 53 in both ends of theupper and lower halves thereof. The fit piece 53 is opened with anengaging hole 54 in the form of a rectangular hole somewhat greater thanthe snap 50. A pair of clamp pieces 55 are provided between the left andright fit pieces 53 while a abutment piece 56 is provided between theclamp pieces 55. Furthermore, cutouts 57 are formed each between the fitpiece 53 and the clamp piece 55 while cutouts 58 are formed each betweenthe clamp piece 55 and the abutment piece 56. By thus proving thecutouts 57, 58, rigidity is reduced in the regions where the cutout 57,58 are formed. The metal fixture 52 is made readily open thicknesswiseof the light-conductor plate 33 by the provision of the cutouts 57, tobe elastically bent at cutout 58 points.

The metal fixture 52 thus structured can be attached in a mannerclamping the point light source 32 and extended region 46 at their bothsurfaces from back of the point light source 52 after fitting the pointlight source 32 in the light-source receiver 47 of the light-conductorplate 33. Namely, as shown in FIG. 17, the slant surface 59 is providedin the snap 50 at its rear part. Accordingly, the metal fixture 52 isattached in a manner clamping partly the point light source 32 andextended region 46 between the upper and lower pieces of the metalfixture 52. When the metal fixture 52 is pushed at its both ends, thefit piece 53 is vertically opened by the slant surface 59 of the snap 50to thereby get over the snap 50, thereby engaging the snap 50 naturallyin the engaging hole 54. The snap 50 has a vertical front face so that,once the snap 50 is engaged in the engaging hole 54, the fit piece 53 iscaught by the snap 50 thus preventing the metal fixture 52 from beingdisengaged.

By thus attaching the metal fixture 52 to the light-conductor plate 33,the clamp pieces 55 of the metal fixture 52 clamp the main and backsurfaces of the thickness-reduced portion between the clamp steps 51 ofthe light-conductor plate 33 and of the thickness-reduced portionbetween the clamp steps 42 of the point light source 32, thus aligningthe point light source 32 thicknesswise (vertically) relative to thelight-conductor plate 33. Specifically, the extended region 46 of thelight-conductor plate 33 has a thickness (maximum thickness) of 0.8 mmwhile the point light source 32 also has a thickness (maximum thickness)of 0.8 mm.

Meanwhile, in the metal fixture 52 attached on the light-conductor plate33, the abutment piece 56 at its tip is in abutment against the pusharea 43 wherein the metal fixture 52 is elastically bent in a bow formas shown in FIG. 11 so that the point light source 32 can be urged ontothe abutment surface 60 by the abutment piece 56 due to an elasticreactive force of the metal fixture 52. Accordingly, even where thereare variations in the size of the point light source 32 or thelight-source receiver 47, the point light source 32 can be accuratelyattached to the light-conductor plate 33 without rattling. Moreover,attachment can be by a one-touch manner without the need to use anadhesive or performing thermal crimp. Meanwhile, because of a dry-type,there is no need of a cure time as required in using an adhesive. Themetal fixture 52 is in a size not to protrude in the main or backsurface of the light-conductor plate 33, similarly to the point lightsource 32. Specifically, the metal fixture 52 is fabricated in anexterior height of 0.6 mm by a stainless steel sheet having a thicknessof 0.1 mm. The depth is 0.2 mm or more in the fixture-fit area 49, theclamp step 51 and the clamp step 42. Accordingly, the metal fixture 52is receded by 0.1 mm relative to the surface of the light-conductorplate 33.

Therefore, according to the surface light source device 31 of theinvention, assembling operation can be simplified for a surface lightsource device 31. Meanwhile, by attaching the metal fixture 52, etc. ina manner not to protrude in the main or back surface of thelight-conductor plate 33, the surface light source device 31 can bereduced in thickness, particularly decreased down to 0.8 mm or smallerin thickness. Furthermore, cost can be rendered low. Meanwhile, themetal fixture 52 can be fixed on the upper and lower surfaces of thelight-conductor plate 33. By elastically urging the point light source32 onto the light-conductor plate 33 through the metal fixture 52, thepoint light source 32 is positively fixed on the light-conductor plate33 thus improving the impact resistance for the surface light sourcedevice 31.

FIG. 18 is a figure showing a characteristic of between a deviation ofbetween a center of light-conductor plate 33 in a height direction and acenter of light-emission window in a height direction (hereinafter,referred to as positional deviation of point light source 32 in height)δ and an incident loss, where the light-emission window has a height(transparent resin 38 height) of 0.7 mm and the light-conductor plate 33has a thickness of 0.7 mm, wherein characteristics are shown for thecases that the gap is 50μ, 30μ and 10μ at between the light incidentsurface 35 of the light-conductor plate 33 and the front surface of thepoint light source 32. In this manner, the incident loss of the lightemitted-from the point light source 32 increases with an increase ofheight positional deviation δ of point light source 32. Meanwhile, incase a variation occurs in the gap size between the light incidentsurface 35 of the light-conductor plate 33 and the point light source32, incident loss also varies. As the gap increases due to variation,the incident loss upon the light-conductor plate 33 increases.

According to the surface light source device 31 of the invention, byutilizing the elasticity of the metal fixture 52, the point light source32 can be urged on the abutment surface 60 of the light-conductor plate33 in a manner free of a gap (although, in this embodiment, no closecontact is provided because of forming prisms in the light incidentsurface 35, close contact can be provided where prisms are notprovided). Moreover, because the point light source 32 is gripped by themetal fixture 52 to accurately align the point light source 32 andlight-conductor plate 33 thicknesswise, the light emitted from the pointlight source 32 less leaks to the outside of the light-conductor plate33 thus enabling to reduce the incident loss and to improve the lightutilization efficiency on the surface light source device 31 using thepoint light source 32. Furthermore, because the point light source 32 isaligned within the dimensional range of the wall thickness of thelight-conductor plate 33 as noted above, the height positional deviationδ of the point light source 32 is reduced to reduce the incident loss.

Meanwhile, according to a method of attaching the point light source 32to the light-conductor plate 33 by use of the metal fixture 52 in thismanner, where replacing or repairing the point light source 32 or thelight-conductor plate 33, by flexing the fit piece 53 of the metalfixture 52 and removed it from the snap 50, the metal fixture 52 can beeasily released to remove the point light source 32 from thelight-conductor plate 33. Then, by using the same metal fixture 52, thereplaced or repaired point light source 32 and light-conductor plate 33can be assembled into the former. Where the point light source 32 isattached by an adhesive or thermal crimp, once the point light source 32is removed from the light-conductor plate 33, the relevant point lightsource 32 and light conductor plate 33 cannot be reused. This recyclenature provide a merit of the invention, contributing to resourcesaving.

FIG. 19 is a figure showing a relationship between a deflection amount εof the metal fixture 52 and the magnitude of a reactive force P thereof.This data is based on the measurement of a reactive force P, i.e. anurge force of the abutment piece 56, upon a deflection in an amount of ξat a central portion of a metal fixture 52 wherein the metal fixture 52is made by a stainless steel sheet having a thickness of 0.1 mm, asshown in FIG. 20. For the surface light source device 31 in the aboveembodiment, urge force P was 4N at a deflection amount ξ of 0.15 mm. Therelationship between a reactive force P and a deflection amount ξ can beadjusted by the depth of the cutout 58.

Meanwhile, although, in the above embodiment, the metal fixture 52 wasbent by abutting the abutment piece 56 against the point light source32, the metal fixture 52 may be elastically bent by abutting a tip ofthe projection 41 against the metal fixture 52.

Meanwhile, the point light source for use in the above embodiment mayuse one in a simplified form as shown in FIG. 21.

Embodiment 2

FIG. 22 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 2 of theinvention. FIG. 23 is a perspective view of a point light source 32 usedfor the surface light source device. In this embodiment, clamp steps 42are formed centrally in the upper and lower surfaces in a backside ofthe point light source 32, and a push area 43, against which theabutment piece 56 of the metal fixture 52 is to be abutted, is formed ina deep surface of the clamp step 42. The light-conductor plate 33 has anextended region 46 having a structure similar to that of embodiment 1.Meanwhile, the metal fixture 52 has clamp pieces 55 made matched to thewidth of the clamp step 51 and hence narrower in width than those ofembodiment 1. Meanwhile, because the upper and lower abutment pieces 56are to clamp the thickness-reduced portion of between the clamp steps 42of the point light source 32 and to abut at their tips against the pusharea 43, the thickness-reduced portion of point light source 32 betweenthe clamp steps 42 has a thickness equal to a distance of between theinner faces of the abutment pieces 56.

Consequently, after putting the point light source 32 in a light-sourcereceiver 47 of the light-conductor plate 33, the metal fixture 52 isattached onto the point light source 32 and extended region 46 from theback of the point light source 32. The thickness-reduced portion, oflight-conductor plate 33 between the clamp steps 51, is clamped andgripped by the clamp pieces 55 while the thickness-reduced portion, ofpoint light source 32 between the clamp steps 42, is clamped by theabutment pieces 56, thereby vertically aligning the point light source32 relative to the light-conductor plate 33 through the metal fixture52. Then, when the metal fixture 52 is pushed at its both sides forward,the snap 50 engages in the engaging hole 54 of the fit piece 53 wherebythe fit pieces 53 is caught by the snap 50. At this time, the abutmentpiece 56 at its tip abuts against the push area 43 of the point lightsource 32, and the metal fixture 52 is elastically bent in a bow form.By the elastic reactive force, the point light source 32 is urged on theabutment surface 60 of the light-conductor plate 33.

In this embodiment, the point light source 32 and the light-conductorplate 33 are gripped by separate portions of the metal fixture 52.Meanwhile, the abutment piece 56 of the metal fixture 52 serves both togrip the point light source 32 and urge the point light source 32 on thelight incident surface 35. Meanwhile, in also this embodiment, the metalfixture 52 is put in the fixture-fit area 49, clamp step 51 of thelight-conductor plate 33 and in the clamp step 42 of the point lightsource 32, not to protrude from the upper and lower surfaces of thelight-conductor plate 33, thus achieving the thickness reduction for thesurface light source device.

Embodiment 3

FIG. 24 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 3 of theinvention. FIG. 25 is a perspective view of a point light source 32 usedfor the surface light source device. In this embodiment, the point lightsource 32 is made low in its upper surface entirety by the same depth asa fixture-fit areas 49 and clamp steps 51. The point light source 32 isformed, at both sides of its lower surface, with clamp steps 42 in thesame depth as the depth of the fixture-fit area 49 and clamp steps 51.Namely, this embodiment uses the point light source 32 that is a thintype. For example, provided that the light-conductor plate 33 has athickness 0.8 mm and the clamp step 51 has a depth 0.2 mm, the pointlight source 32 has a thickness 0.6 mm and the clamp step 42 has a depth0.2 mm. When the point light source 32 is put in a light-source receiver47, the upper-side clamp step 51 and the point light source 32 are flushat their upper surfaces while the lower-side clamp step 51 and the clampstep 42 of the point light source 32 are flush at their lower surfaces.

The light-conductor plate 33 has an extended region 46 having astructure similar to that of embodiment 1. Although the metal fixture 52also has a structure similar to that of embodiment 1, the abutmentpieces 56 are bent inward so that the light emitting element 37 withinthe point light source 32 can be pushed in its position.

Consequently, after putting the point light source 32 in thelight-source receiver 47 of the light-conductor plate 33, in case themetal fixture 52 is attached onto the point light source 32 and extendedregion 46 from back of the point light source 32, the clamp pieces 55clamp and hold the thickness-reduced portion of light-conductor plate 33between the clamp steps 51, the upper surface of and thickness-reducedportion between the clamp steps 42 of the point light source 32, therebyvertically aligning the point light source 32 relative to thelight-conductor plate 33 by means of the metal fixture 52. Then, in casethe metal fixture 52 is pushed at its both sides forward, the snaps 50engage in the engaging holes 54 of the fit pieces 53 whereby the fitpiece 53 is caught by the snap 50. At this time, the abutment piece 56at its tip abuts against a backside central region of the point lightsource 32, and the metal fixture 52 is elastically bent in a bow form.By the elastic reactive force, the point light source 32 is urged on thelight incident surface 35 of the light-conductor plate 33.

In case the point light source 32 can be reduced in thickness as in thisembodiment, the clamp steps 42 of the point light source 32 can beprovided in any one of the upper and lower surfaces. Furthermore, incase the point light source 32 can be reduced in thickness, it can beused in a form (rectangular) as it is without forming recesses for clampsteps 42 in the point light source 32, which can cope with the thin-typepoint light source 32. However, because the point light source 32 at itslower surface is mounted on a flexible printed board 45, this embodimentis reduced in the thickness only at the upper surface side.

Incidentally, in the foregoing embodiments, the fit piece 53 of themetal fixture 52 is opened with engaging hole 54 to engage the snap 50therein. However, as shown in FIGS. 26 and 27, the fit piece 53 of themetal fixture 52 may be formed in an L-form or in a hook form, to engagethe snap 50 from one side. The use of a metal fixture 52 in such a form,the metal fixture 52 can be shortened in length to reduce the space forattaching the metal fixture 52. Meanwhile, because in this embodimentthe sidewall face of the snap 50 is formed integral with the innerperipheral wall surface of the metal fixture 49 as shown in FIG. 26, thesnap 50 increases its strength to improve the attachment strength of themetal fixture 52. Meanwhile, as shown in FIGS. 28 and 29, the fit piece53 of the metal fixture 52 may be formed in a T-form so that the fitpiece 53 can engage with two snaps 50 arranged adjacently. Meanwhile,the snaps 50 have respective side faces formed integral with the innerperipheral wall surface of the metal fixture 49. In such an embodiment,the strength of the snap 50 increases. Moreover, because the fit piece53 is caught and held by two snaps 50, the attachment strength of themetal fixture 52 increases to hold the point light source 32 at greaterurging force.

Embodiment 4

FIG. 30 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 4 of theinvention. In this surface light source device, an extended region 46 isprovided centrally in a shorter side of an outer peripheral surface ofthe light-conductor plate 33, to provide a light-source receiver 47centrally in the extended region 46. In a deep surface of thelight-source receiver 47, a light incident surface 35 is formed toprovide a projection 48 protruding in a side surface of the light-sourcereceiver 47. Meanwhile, snaps 50 protrude respectively in left and rightsurfaces of the extended region 46. On the both sides of thelight-source receiver 47, clamp steps 51 are recessed in the upper andlower surfaces of the extended region 46.

The point light source 32, using a structure explained in embodiment 1,is recessed with clamp steps 42 respectively in the upper and lowersurfaces at rear left and right sides, wherein a push area 43 is formedin a backside center of the point light source,32.

A metal fixture 52 is worked by bending a metal material of a stainlesssteel sheet, a steel sheet, an aluminum sheet or the like, and bent in abow form in plan. The metal fixture 52 has both-side pieces bent forwardto be parallel with each other into fit pieces 53. The fit piece 53 isopened with an engaging hole 54 in a tip thereof. Meanwhile, the metalfixture 52 has a central portion made as an abutment piece 56 bentforward in a swelling fashion. On the both sides of the abutment piece56, clamp pieces 55 extend forward from its upper and lower portionsthereof.

Consequently, in this embodiment, after putting the point light source32 in the light-source receiver 47 of the light-conductor plate 33, themetal fixture 52 is attached onto the point light source 32 and extendedregion 46 from back of the point light source 32. By the clamp pieces55, clamped are the interval between the clamp steps 51 of thelight-conductor plate 33 and the clamp steps 42 of the point lightsource 32, to grip those together. By means of the metal fixture 52, thepoint light source 32 is vertically aligned relative to thelight-conductor plate 33. Then, when the metal fixture 52 is pushedforward, the snap 50 engages in the engaging hole 54 of the fit piece 53and the fit piece 53 is caught by the snap 50. At this time, theabutment piece 56 abuts against the push area 43 of the point lightsource 32 thereby elastically deforming the metal fixture 52. By theelastic reactive force, the point light source 32 is urged on the lightincident surface 35 of the light-conductor plate 33.

In also this embodiment, the height of the metal fixture 52 is smallerthan the thickness of the light-conductor plate 33. Particularly, theexterior height at between the upper and lower clamp pieces 55 issmaller than the thickness of the light-conductor plate 33. Because theclamp pieces 55 grip the clamp steps 51 of the light-conductor plate 33and the clamp steps 42 of the point light source 32, the metal fixture52 does not protrude from the upper and lower surfaces of thelight-conductor plate 33, thus achieving the thickness reduction for thesurface light source device.

Embodiment 5

FIG. 31 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 5 of theinvention. In this surface light source device, a light-source receiver47 is provided in an outer peripheral surface of the light-conductorplate 33 at a center in a shorter side thereof. In a deep surface of thelight-source receiver 47, a light incident surface 35 is formed. Aprojection 48 protrudes in the side surface of the light-source receiver47. Meanwhile, on the left and right sides of the light-source receiver47, there are provided fixture-fit areas 49 having a depth nearly a halfof the thickness of the light-conductor plate 33. Crimp pins 61 areprovided standing in the bottom surfaces of the fixture-fit areas 49.

A metal fixture 52 is formed in generally a squared-U form by a tabularmetal plate, having, at both ends, fit pieces 53 whose tips are openedwith snap-formed engaging holes 54 partly released. Meanwhile, somewhatinner than the fit pieces 53 in the metal fixture 52, cutouts 62 areprovided to provide elasticity to the metal fixture 52. Meanwhile, in abackside of a point light source 32, there is cut throughout the width apositioning slit 63 having a vertical width equal to the thickness ofthe metal fixture 52. Incidentally, the slit cross-sectional form may bea V-groove.

Consequently, in this embodiment, after putting the point light source32 in the light-source receiver 47 of the light-conductor plate 33, themetal fixture 52 is positioned in back of the point light source 32 andthe metal fixture 52 is fit in the positioning slit 63 of the pointlight source 32, and the engaging hole 54 of the fit piece 53 is fitover the crimp pin 61 in a snap manner. Then, the crimp pin 61 isthermally crimped to thereby fix the metal fixture 52 to thelight-conductor plate 33, thus preventing the metal fixture 52 fromfloating. In the state the metal fixture 52 is fixed on thelight-conductor plate 33, the metal fixture 52 is elastically bent inthe positions of cutouts 62. By the elastic reactive force, the pointlight source 32 is urged on the light incident surface 35 of thelight-conductor plate 33. Meanwhile, the fit piece 53 of the metalfixture 52 is vertically aligned by the fixture-fit area 49 and fixed bythe crimp pin 61. The point light source 32 is vertically aligned byfitting the metal fixture 52 in the positioning slit 63, thus verticallyaligning the point light source 32 and the light-conductor plate 33.Accordingly, this embodiment also can eliminate the positional variationin attaching the point light source 32 and hence improve lightutilization efficiency. Meanwhile, the metal fixture 52 is in a plateform and hence not to protrude in the upper or lower surface of thelight-conductor plate 33, thus enabling to reduce the thickness of thesurface light source device. Meanwhile, the use of such a structure ofmetal fixture 52, component cost can be lowered.

Although not shown, this embodiment can use a wire material, such as apiano wire, in place of the metal fixture 52 in the above plate form.Namely, a wire material, as a metal fixture 52, at its one end is woundover the crimp pin 61 and the crimp pin 61 is thermally crimped to fixthe one end of the wire material. Then, the wire material is passedthrough the positioning slit 63 of the point light source 32. Whileapplying a tension to the wire material, the other end thereof isconnected to the crimp pin 61, and the crimp pin 61 is thermally crimpedwith the wire material thereby fixing the other end of the wirematerial. In such a modification, the point light source 32 can be urgedon the light-conductor plate 33 by the tension through the wirematerial. Meanwhile, by stretching the wire material, the point lightsource 32 can be vertically aligned.

Embodiment 6

FIG. 32 is an exploded perspective view showing, with magnification, apart of a surface light source device according to embodiment 6 of theinvention. In this surface light source device, an extended region 46protrudes centrally in a shorter side, in an outer peripheral surface ofthe light-conductor plate 33, to provide a light-source receiver 47 inthe center of the extended region 46. In a deep surface of thelight-source receiver 47, a light incident surface 35 is formed to havea projection 48 protruding in a side surface of the light-sourcereceiver 47. Meanwhile, crimp pins 61 project horizontally in the outerperipheral surface of the light-conductor plate 33 in a mannersandwiching the extended region 46.

The point light source 32 has a thickness equal to or smaller than thethickness of the light-conductor plate 33. The point light source 32 hasa depth greater than the depth of the light-source receiver 47 so that,when the point light source 32 is put in the light-source receiver 47, apush area 43 positioned in the rear end of the point light source 32protrudes from the light-source receiver 47. Furthermore, a positioningprojection 64 protrudes centrally in the push area 43.

The metal fixture 52 is worked by bending a strip metal sheet, having aheight (width of the strip metal plate) equal to or smaller than thethickness of the light-conductor plate 33. The metal fixture 52 is bentalong a contour extending from a region left to the extended region 46of the light-conductor plate 33 to a region right to the extended region46 through the extended region 46. In the fit pieces 53 positioned inthe respective ends, crimp holes 65 are opened with a diameter equal tothe diameter of the crimp pin 61. The metal fixture 52, at its center,is opened with a positioning hole 66 having a diameter equal to thediameter of the positioning projection 64. Incidentally, the crimp holes65 and positioning hole 66 may be made horizontally long in order toabsorb pitch errors.

Consequently, in this embodiment, after putting the point light source32 in the light-source receiver 47 of the light-conductor plate 33, themetal fixture 52 is positioned in back of the point light source 32 andextended region 46. The crimp pin 61 is fit in the crimp hole 65 of themetal fixture 52 while the positioning projection 64 is fit in thepositioning hole 66, to thermally crimp the crimp pin 61 to the metalfixture 52, thus fixing the metal fixture 52 to the light-conductorplate 33 and vertically aligning the point light source 32 by means ofthe metal fixture 52.

In this state, the metal fixture 52 is vertically aligned relative tothe light-conductor plate 33 by the fitting of the crimp pin 61 and thecrimp hole 65. The point light source 32 is vertically aligned relativeto the metal fixture 52 by the fitting of the positioning projection 64and the positioning hole 66. As a result, the point light source 32 isaccurately aligned thicknesswise of the light-conductor plate 33.Meanwhile, the push area 43 of the point light source 32 protrudes fromthe extended region 46 whereby the metal fixture 52 at its center abutsagainst the push area 43 thus being pushed back. By the elastic reactiveforce of the metal fixture 52, the point light source 32 is urged on thelight incident surface 35 of the light conductor plate 33.

In the embodiment like this, the metal fixture 52 is prevented fromprotruding from the upper and lower surfaces of the light-conductorplate 33 by making the height of the metal fixture 52 smaller than thethickness of the light-conductor plate 33, thus enabling to reduce thethickness of the light-conductor plate 33. Furthermore, the metalfixture 52 can be fabricated by merely bending a strip metal plateopened with a crimp hole 65 and positioning hole 66, thus rendering thecost low.

Incidentally, the above embodiment provided the positioning projection64 on the point light source 32, and the positioning hole 66 in themetal fixture 52. Conversely, the positioning hole 66 may be provided inthe point light source 32 while a positioning projection 64 be in themetal fixture 52.

Embodiment 7

In the invention, a plurality of point light sources 32 may be attachedby means of one metal fixture 52. For example, FIG. 33 is an explodedperspective view showing, with magnification, a part of a surface lightsource device according to embodiment 7 of the invention. In thissurface light source device, two light-source receivers 47 are recessedside by side in a light-conductor plate 33, to form clamp steps 67 inthe upper and lower surfaces of between the both light-source receivers47. Clamp steps 51 and fixture-fit areas 49 are provided on the outersides of those. The fixture-fit areas 49 are respectively provided withsnaps 50.

The two point light sources 32 are those as shown in FIG. 21, forexample, wherein clamp steps 42 are formed on both sides in the upperand lower surface while a push area 43 is provided in a backsidethereof.

A metal fixture 52 is provided with fit pieces 53 having engaging holes54 at respective ends, clamp pieces 55 on the inner side thereof,abutment pieces 56 on the inner side thereof, and broad clamp pieces 55between the abutment pieces 56. Cutouts 57 are formed between theengaging hole 54 and the clamp piece 55 while cutouts 58 are formedbetween the clamp piece 55 and the abutment piece 56.

Consequently, after putting the point light sources 32 respectively inthe light-source receivers 47 of the light-conductor plate 33, the fitpiece 53 is engaged on the snap 50 in the fixture-fit area 49 therebyattaching the metal fixture 52 to the light-conductor plate 33. Theclamp pieces 55, on the both sides, clamp and grip the thickness-reducedportion between the clamp steps 51 of the light-conductor plate 33 andthe thickness-reduced portion between the clamp steps 42 of the pointlight source 32. The central clamp pieces 55 clamp and grip thethickness-reduced portion between the clamp steps 67 of thelight-conductor plate 33 and the thickness-reduced portion between theclamp steps 42 of the point light source 32. Due to this, the pointlight sources 32 are aligned thicknesswise relative to thelight-conductor plate 33. Meanwhile, the point light sources 32 arerespectively urged on the light incident surfaces 35 by abutting theabutment pieces 56 of the elastically deflected metal fixture 52 againstthe push area 43 of the point light sources 32.

Although, here, the two point light sources 32 were attached by onemetal fixture 52, three or more point light sources 32 can be attached.By attaching a plurality of point light sources 32 by one metal fixture52, assembling can be simplified and cost be lowered. Meanwhile,although the above illustrated embodiment used the plurality of pointlight sources 32 with the structure as in embodiment 1, a plurality ofpoint light sources 32 can be naturally attached also in another of theembodiments.

Embodiment 8

FIG. 34 is a perspective view showing, with magnification, a part of asurface light source device according to embodiment 8 of the invention.FIG. 35 is an exploded perspective view showing, with magnification, apart of the surface light source device. FIG. 36 is an explodedperspective view showing, with magnification, a part of the surfacelight source device, which is in a different direction. The point lightsource 32 used in this embodiment is structured similarly to the pointlight source 32 (FIG. 25) used in embodiment 3. Namely, the point lightsource 32 in embodiment 8, although formed with somewhatconcavo-convexes in the upper surface, is formed with clamp steps 42 onboth sides only in the lower surface instead of in the upper surfacethereof. The point light source 32 is reduced in thickness by notproviding clamp steps 42 in the upper surface of the point light source32. Specifically, the point light source 32 has a thickness 0.6 mm.Namely, provided that the point light source 32 structured as in FIG. 21has a thickness 0.8 mm, the thickness of the point light source 32 canbe given 0.6 mm by removing the point light source 32 of its protrudingportion, at the upper surface thereof, from the clamp step 42.Incidentally, the clamp step 42 in the lower surface of the point lightsource 32 has a depth equal to the thickness 0.1 mm of the metal fixture52.

Meanwhile, although the light-conductor plate 33 in embodiment 3 has athickness 0.8 mm greater than the point light source 32, thelight-conductor plate 33 in embodiment 8 has a thickness 0.5 mm that issmaller than the point light source 32. Meanwhile, in embodiment 8,clamp steps 51 and fixture-fit areas 49 are recessed on both sides ofthe light-source receiver 47, in both surfaces of the light-conductorplate 33. In the upper surface of the light-conductor plate 33, snaps 50project in the fixture-fit areas 49 in a manner protruding from theouter side surfaces. In the lower surface of the light-conductor plate33, snaps 50 project in the fixture-fit areas 49 in a manner protrudingfrom the inner side surfaces.

In this embodiment, because the clamp steps 42 are not provided in theupper surface of the point light source 32, in case the point lightsource 32 is held at its both surfaces by a metal fixture 52 as inembodiment 1-7, the metal fixture 52 protrudes above the point lightsource 32 and light-conductor plate 33 thus increasing the thickness ofthe surface light source device. For this reason, in the lower surfaceside where clamp steps 42 are provided in the point light source 32, theclamp steps 42 of the point light source 32 and the clamp steps 51 ofthe light-conductor plate 33 are held from below by clamp pieces 55 ofthe metal fixture 52 similarly to embodiment 1-7. However, in the uppersurface side where clamp steps 42 are not provided in the point lightsource 32, embodiment 8 holds only the clamp steps 51 of thelight-conductor plate 33 from above by means of clamp pieces 55 of themetal fixture 52 in embodiment 8. The clamp pieces 55 of the metalfixture 52 do not hold the upper surface of the point light source 32.

Consequently, a cutout 68 is provided in a position corresponding to thepoint light source 32, in the upper-surface clamp piece 55 of the metalfixture 52 as shown in FIGS. 35 and 36, in a manner not to overlap withthe point light source 32 when attached to the light-conductor plate 33.In the upper surface side, the clamp piece 55 is made in a manneravoiding the position for the point light source 32. As a result, themetal fixture 52 can be given a thickness of 0.6 mm similarly to thepoint light source 32.

Meanwhile, the point light source 32 is previously mounted, by a solder,on a flexible printed board 45 sufficiently greater as compared to theplanar surface area of the point light source 32 or the light-sourcereceiver 47. When attaching the point light source 32 to thelight-conductor plate 33, the point light source 32 mounted on theflexible printed board 45 is put in the light-source receiver 47 frombelow. In case the point light source 32 is put in the light-sourcereceiver 47, when the flexible printed board 45 comes into abutmentagainst the lower surface of the light-conductor plate 33, the pointlight source 32 no longer moves upward. Moreover, design is made suchthat, when the flexible printed board 45 goes into abutment against thelower surface of the light-conductor plate 33, the point light source 32takes a desirable vertical position for the light incident surface 35 ofthe light-conductor plate 33.

Then, as shown in FIG. 34, the metal fixture 52 is attached to thelight-conductor plate 33 from back of the point light source 32. At thistime, the lower clamp piece 55 of the metal fixture 52 is inserted tobetween the clamp step 42 of the light source 32 and the flexibleprinted board 45. In the state the contact piece 56 of the metal fixture52 is abutted against the back surface of the point light source 32, thefit piece 53 of the metal fixture 52 is engaged on the snap 50 of thelight-conductor plate 33. The metal fixture 52 at its upper and lowerclamp pieces 55 grips the upper and lower clamp steps 51 of thelight-conductor plate 33. This vertically aligns the metal fixture 52relative to the light-conductor plate 33.

In the state the point light source 32 is attached on thelight-conductor plate 33 by the metal fixture 52, the point light source32 at its front surface is urged on the abutment surface 60 of thelight-conductor plate 33 through the elasticity of the point lightsource 32 whereby the point light source 32 is aligned in a front-reardirection. The projection 48, in the side surface of the light-sourcereceiver 47, abuts against a side surface of the point light source 32thus aligning the point light source 32 in a left-right direction.Furthermore, the lower clamp piece 55 of the point light source 32 holdsthe clamp step 42 in the lower surface of the point light source 32thereby preventing the point light source 32 from being detacheddownward from the light-source receiver 47. Because the clamp piece 55in the upper surface of the metal fixture 52 is provided avoiding thepoint light source 32, the point light source 32 cannot be held fromabove by a certain metal fixture 52. However, the point light source 32is regulated not to be detached upward from the light-source receiver 47by the abutment of the flexible printed board 45 against the lowersurface of the light-conductor plate 33. Accordingly, in thisembodiment, the point light source 32 can be vertically aligned by thecooperation of the clamp pieces 55 in the lower surface of the metalfixture 52 and the flexible printed board 45. Furthermore, thicknessreduction is available for the surface light source device.

In the metal fixture 52 of such a structure, structure is not symmetricvertically but shape is different between the upper surface side and thelower surface side. Consequently, in case the metal fixture 52 isattached incorrect vertically during attaching of the point light source32 to the light-conductor plate 33, the point light source 32 is to passthe cutout 68 of the clamp piece 55 and fall down, together with theflexible printed board 45, out of the light-source receiver 47 becausethe point light source 32 at its lower surface is not held by the clamppiece 55. For this reason, in this embodiment, the fit piece 53 on theupper surface side is bent L-form directed outward while the fit piece52 on the lower surface side is bent L-form directed inward.Correspondingly, in the light-conductor plate 33, the snap 50, in thefixture-fit area 49 on the upper surface side, protrudes inward from theouter side surface of the left and right side surfaces. The snap 50, inthe fixture-fit area 49 on the lower surface side, protrudes outwardfrom the inner side surface of the left and right side surfaces.Accordingly, in the case the metal fixture 52 is correct vertically (asto main or back surface), the upper and lower fit pieces 53 can berespectively engaged on the upper and lower snaps 50 of thelight-conductor plate 33. However, when the metal fixture 52 isincorrect vertically (as to main or back surface), the upper and lowerfit pieces 53 cannot be respectively engaged on the upper and lowersnaps 50 of the light-conductor plate 33. Based on this, the point lightsource 32 is prevented from disengaging due to incorrectly directedmetal fixture 52.

1. A surface light source device characterized by comprising: alight-conductor plate that conducts light at an interior and allows sameto exit at a light-exit surface to an outside; and a light sourcearranged oppositely to a light incident surface of the light-conductorplate and small in size as compared to a width of the light-conductorplate; the light source being held by a fixture engaged on thelight-conductor plate, the fixture in part being elastically abuttedagainst an opposite surface of the light source to a surface thereoffacing to the light incident surface thereby urging the light source onthe light incident surface.
 2. A surface light source device accordingto claim 1, wherein the light source has a light-emission window havinga height thicknesswise of the light-conductor plate equal to or smallerthan a thickness of the light-conductor plate.
 3. A surface light sourcedevice according to claim 1, wherein the fixture has an exterior heightthicknesswise of the light-conductor plate equal to or smaller than athickness of-the light-conductor plate.
 4. A surface light source deviceaccording to claim 1, wherein the fixture has a shape symmetric in180-degree-rotation about an attaching direction to the light-conductorplate.
 5. A surface light source device according to claim 1, whereinthe fixture is removably attached on the light-conductor plate.
 6. Asurface light source device according to claim 5, wherein the fixture isfixed on the light-conductor plate by recessing fixture-fit areas inupper and lower surfaces of the light-conductor plate, providing catchesprojecting in the fixture-fit areas, providing fit pieces in a ringform, an L-form or T-form in the fixture formed in a folded-double form,and putting the fit pieces on the fixture-fit areas into engagement onthe catches.
 7. A surface light source device according to claim 5,wherein the fixture is fixed on the light-conductor plate by providingcatches in a side surface of the light-conductor plate, and engaging, onthe catches, the fit pieces in a ring form, an L-form or T-form providedin the fixture.
 8. A surface light source device according to claim 1,wherein the fixture is fixed on the light-conductor plate by forming oneof a crimp projection or crimp hole in any of a fixture-fit arearecessed in an upper surface or a lower surface of the light-conductorplate, a side surface of the light-conductor plate and a front surfaceof the light-conductor plate, forming other of the crimp projection orthe crimp hole in the fixture, and inserting the crimp projection in thecrimp hole into crimping.
 9. A surface light source device according toclaim 1, wherein the fixture and the light-conductor plate have aligningmeans for aligning the fixture and the light-conductor plate to eachother thicknesswise of the light-conductor plate, the fixture and thelight source having aligning means for aligning the fixture and thelight source to each other thicknesswise of the light-conductor plate.10. A surface light source device according to claim 9, wherein meansfor aligning the fixture and the light-conductor plate is constituted byproviding a thickness-reduced portion in a vicinity of the lightincident surface of the light-conductor plate, and clamping thethickness-reduced portion by a pair of parallel protuberances providedin the fixture.
 11. A surface light source device according to claim 9,wherein means for aligning the fixture and the light-conductor plate isconstituted by forming one of a positioning projection or a positioninghole in any of a recess provided in an upper surface or an lower surfaceof the light-conductor plate, a side surface of the light-conductorplate and a front surface of the light-conductor plate, forming other ofthe positioning projection or the positioning hole in the fixture, andfitting the positioning projection in the positioning hole.
 12. Asurface light source device according to claim 9, wherein means foraligning the fixture and the light source is constituted by providing athickness-reduced portion at least in a part of the light source, andclamping the thickness-reduced portion by a pair of parallelprotuberances provided in the fixture.
 13. A surface light source deviceaccording to claim 9, wherein means for aligning the fixture and thelight source is constituted by forming one of a positioning projectionor a positioning hole in any of a recess provided in an upper surface oran lower surface of the light source, a side surface of the light sourceand a front surface of the light source, forming other of thepositioning projection or the positioning hole in the fixture, andfitting the positioning projection in the positioning hole.
 14. Asurface light source device according to claim 9, wherein means foraligning the fixture and the light source is constituted by forming apositioning slit in a back surface of the light source, and fitting apart of the fixture in the positioning slit.